Metal casting apparatus with means for evacuating mold chamber and pouring chamber

ABSTRACT

Apparatus is provided for casting molten metal into a mold under a vacuum. The apparatus includes a pair of housings which are movable together to form a sealed enclosure having an upper portion defining a pouring chamber and a lower portion defining a mold chamber adapted to be sealed from the pouring chamber around the mold. Both chambers may be evacuated during the casting operation.

O United States Patent 1 91 [111 3,800,851

Coghill Apr. 2, 1974 [54] METAL CASTING APPARATUS WITH 3,336,970 8/1967 Watts et al 164/62 MEANS O EVACUATING MOLD 3,677,332 7/1972 Smiernow 164/62 CHAMBER AND POURING CHAMBER 3,705,615 12/1972 Watts 164/62 [75] Inventor: Timothy L. Coghill, Mentor, Ohio FOREIGN PATENTS OR APPLICATIONS 847,862 9/1960 Great Britain 164/254 [73] Ass1gnee: Preclsion Metalsmiths, Inc., 353,411 11 1960 Great Britain Cleveland, Ohio 384,783 2/1965 Switzerland 164/65 [22] Filed: May 1971 Primary ExaminerRobert D. Baldwin [21] Appl. No.: 147,828 Attorney, Agent, or FirmWatts, Hoffmann, Fisher &

. Heinke [52] 11.8. C1 164/255, 164/256, 164/258 51 1m. 01 1122a 27/14, B22d 27/15 [57] ABSTRAT [58] Field of Search U 164/254, 255 256, 258 Apparatus is provided for casting molten metal into 21 164/61, 62 65, 412 210; 104/79 mold under a vacuum. The apparatus includes a pair of housings which are movable together to form a [56] References Cited sealed enclosure having an upper portion defining a UNITED STATES PATENTS pouring chamber and a lower portion defining a mold chamber adapted to be sealed from the pouring chama g her around the mold. Both chambers may be evacue s er e a 3,169,285 2/1965 Hatch et al. 164/210 x med dunng the castmg 2,806,271 9/1957 Operhall 164/65 X 15 Claims, 9 Drawing Figures PATENTEDAPR 2 m4 SHEEY 1 BF 5 Fig. I

Fig.3

INVENTOR. TIMOTHY L, COGH/LL BY m, W7 5 a Mz ATTOENEYE ATENTED R 1914 SHEET 2 OF 5 Fig. 4

Fig. 5

INVENTOR. T/MUTHY L, CUGH/LL 4TTO/2NEY5 "ATENTEBAPR 21914 SHEET 3 BF 5 INVENTOR. T/lWOTHY L, COGH/LL BY 9%, m, i We,

' ATTOENEKE METAL CASTING APPARATUS WITH MEANS FOR EVACUATING MOLD CHAMBER AND POURING CHAMBER BACKGROUND OF THE INVENTION This invention relates generally to metal casting apparatus, and more specifically to apparatus for casting investment molds, both shell molds and bulk investment molds.

The present invention is particularly concerned with providing apparatus for carrying out the methods disclosed in U.S. application Ser. No. 96,517 of Claude H. Watts entitled METAL CASTING PROCESSES WITH VACUUM AND PRESSURE, filed Dec. 9, 1970, now U.S. Pat. No. 3,705,615 issued Dec. 12, 1972, and assigned to a common assignee. The referenced application discloses a method of casting which comprises the steps of placing a mold in a mold chamber so that the opening of the mold communicates with the vacuum casting or pouring chamber which is sealed from the mold chamber, evacuating the vacuum casting chamber and then introducing molten metal into the opening of the mold to fill a cavity, thereafter restoring the casting chamber to atmospheric pressure while the metal in the mold is still molten, and applying a vacuum to the outside of the mold by evacuating the mold chamber prior to solidification of the metal, and more preferably prior to introducing the metal into the mold.

The casting technique described above can be used to cast many different kinds of metals, and may be found particularly advantageous in producing castings having thin wall sections. The technique is especially suited for casting metals including aluminum alloys and the like which are subject to air entrapment, porosity and drawback.

SUMMARY OF THE INVENTION An object of the present invention is to provide apparatus for casting gas permeable molds, especially investment molds, under a vacuum.

A more specific object of the invention is to provide apparatus for casting a gas permeable mold, especially an investment mold, by a procedure including the steps of introducing molten metal while under a vacuum into an opening of the mold to fill a cavity, thereafter increasing the pressure on the molten metal through the mold opening, and applying a vacuum to the outside of the mold during solidification of the metal.

The foregoing objects of the invention are attained by the provision of an apparatus comprising an upper housing and a lower housing which are movable into cooperable engagement to form a sealed enclosure having an upper portion defining a pouring chamber and a lower portion defining a mold chamber adapted to be sealed from the pouring chamber around the mold. Vacuum lines are connected to at least one of the housings for permitting the chambers to be evacuated, and metal pouring means, such as a ladle, a furnace or the like, is provided in the upper housing for introducing molten metal into a mold sealed in the mold chamber.

In the preferred embodiments of the invention, the upper housing is movable along the rails of a track assembly. The track assembly is adapted to be raised and lowered adjacent the lower housing. In operation the track assembly is elevated to lift the upper housing from the lower housing so that the upper housing can be rolled to a position which permits a mold to be placed into and removed from the lower housing. When the mold has been sealed in the lower housing, the upper housing is returned to a position over the lower housing and the track assembly is lowered to place the upper housing in sealed engagement with the lower housing.

In one embodiment of the invention, the apparatus includes a pair of lower housings. The upper housing is selectively cooperable with each of the lower housings to form a sealed enclosure so that casting operations can be alternately carried out in each of the lower housings. In another embodiment of the invention which is especially suitable for casting ferrous metals, an induction melting furnace is provided in the upper housing. The induction furnace is tiltably mounted so that it can be used to pour molten metal into the mold sealed in the mold chamber.

Other objects, advantages and a fuller understanding of the invention will be had from the following detailed description when taken in conjunction with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view of a preferred embodiment of the invention;

FIG. 2 is an end elevational view taken in the plane of the line 22 of FIG. 1;

FIG. 3 is an opposite end elevational view of the apparatus shown in FIG. 1;

FIG. 4 is a top plan view with portions broken away and eliminated of the embodiment shown in FIG. 1;

FIG. 5 is a vertical cross-sectional view taken substantially on the line 55 of FIG. 4;

FIG. 6 is a side elevational view of another embodiment of the invention;

FIG. 7 is a side elevational view of still another embodiment of the invention;

FIG. 8 is an end elevational view taken in the plane of line 8--8 of FIG. 7; and

FIG. 9 is an enlarged, vertical plan view, partially in cross-section and with portions eliminated, of the apparatus shown in FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, a preferred embodiment of the invention especially suitable for casting non-ferrous metals is illustrated in FIGS. 1-5 and is designated by reference numeral 15. The apparatus 15 is generally comprised of a support structure 16 which includes a track assembly 17. A housing 18 is secured to the support structure 16 and cooperates with a housing assembly 19 to form a sealed enclosure. The housing assembly 19 is movable along the track assembly 17 above the housing 18.

The support structure 16 is defined by structural members which are welded together to form a rigid framework including upper and lower side members 25. The members 25 are connected together at one end of the framework by crosspieces 26, 27 and vertical struts 28. The housing 18 is mounted near the other end of the framework by vertical struts 29 which are connected between the upper and lower members 25 and are welded to the sides of the housing. The lower members 25 of the framework are extended beyond the housing 18 by extension members which are con nected by a cross member 31. Casters 32 are suitably connected to the underside of the framework to support it for movement.

In the embodiment of the invention illustrated in FIGS. 1-5, the track assembly 17 has one end pivotally connected to the support structure 16 and the other end of the track assembly is adapted to be raised and lowered adjacent the housing 18. The track assembly 17 comprises a pair of rails extending on opposite sides of the housing 18. As is best shown in FIG. 3, a tube 41 is secured to an end of each of the rails 40 and is rotatably engaged on a bar 42. The bar 42 extends across the support structure 16 and is secured to the cross piece 26. The opposite ends of the rails 40 are connected by a cross member 43. An air cylinder actuator 44 is mounted by a plate 45 secured to the cross member 31 of the support structure 16, and the piston rod of the air cylinder is connected to the cross member 43 between the rails 40. The air cylinder 44 is suitably connected to a source of compressed air, and a valve (not shown) is provided for actuating the air cylinder to raise and lower the track assembly 17 by tilting it about the pivot bar 42. In the illustrated construction of the track assembly, angle members 46 are connected to the undersides of the rails 40 and slidably engage the vertical struts 29.

The upper housing assembly 19 is movably supported on the rails 40 by wheels 47. When the air cylinder 44 has been actuated to raise the track assembly 17, the housing assembly 19 is movable along the rails between the broken line position shown in FIG. 1 and a position above the housing 18 in which the housing assembly 19 may be lowered into cooperative engagement with the housing 18 by lowering the track assembly. A pair of cushioned stop assemblies is provided for engaging the housing assembly 19 in the broken line position of FIG. 1. Each of the stop assemblies includes a tube 55 which is fixed to a bracket 56 extending upwardly from the support structure 16. A plunger 57 is slidable in the tube 55 and has a head portion engageable by a bracket 58 on the housing assembly 19. The plunger 57 is biased toward the housing assembly by a spring 59 which is mounted around the plunger between its head and the bracket 56.

As generally described above, the upper housing assembly 19 is movable into cooperative engagement with the lower housing 18 by lowering the track assembly 17 to form a sealed enclosure. Referring to FIG. 5, the enclosure is shown to have an upper portion which defines a pouring or casting chamber 65 and a lower portion which defines a mold chamber 66. The mold chamber 66 is adapted to be sealed from the pouring chamber 65 around a mold supported in the housing 18.

The housing 18 has a lower section 67 which defines the mold chamber 66 and an enlarged diameter, upper section 68 having a radial flange 69. The cylindrical wall of the housing section 68 may be provided with an asbestos lining 70, if desired. A platform 71 is provided within the housing section 67 for supporting a mold. The platform 71 may be comprised of a metal plate 72 on which is disposed a gasket 73. Suitable gaskets may be made from asbestos pads, insulation or blankets formed of refractory fibers, such as alumina-silica fibers, and the like. A hole 74 is formed through the plate 72 and the gasket 73, and the plate 72 is supported above the bottom of the housing 18 by suitable supports 75. The height of the supports 75 is preferably adjustable so that the top of the mold supported on the platform 71 can be positioned in the desired plane.

The upper housing assembly 19 includes a cylindrical section which cooperates with the housing section 68 to define the pouring or casting chamber 65. The cylindrical section 85 has an open lower end and an upper end which is closed by a removable plate. The removable plate closing the upper end of the cylindrical section 85 is provided with a window 86 through which an operator can observe the casting operation. A plate 87 is secured around the open lower end of the section 85 and is adapted to be supported by the flange 69 of the housing 18. A sealing gasket of ring 88 is provided between the flange 69 and the plate 87. The wheels 47 are connected to the plate 87 by brackets 89.

A pouring ladle is mounted in the chamber 65 for pouring molten metal into a mold supported in the mold chamber 66. The ladle 95 is mounted in a housing section 96 secured to the section 85, and the spout 97 of the ladle projects into the section 85 through an opening 98 in its side wall. The ladle 95 is mounted for tilting movement by a cradle 100. The cradle 100 is secured to a rotatable rod 101 which is journalled in the sides of the housing section 96 and has an external handle 102. An opening 103 is provided in the housing section 96 above the ladle 95 so that the ladle can be filled with metal. The opening 103 is closed by a removable cover plate 104 having a handle 105.

Each of the chambers 65, 66 is capable of being evacuated during the casting operation. As shown in FIGS. 1 and 2, a vacuum line or conduit extending from a suitable vacuum source is connected to the housing 18 in communication with the mold chamber 66. A three-way valve 111 in the conduit 110 is actuatable to connect the chamber 66 to the vacuum source and to the atmosphere. Another vacuum line or conduit 112 is connected to the upper section 68 of the housing 18 in communication with the pouring chamber 65 and a three-way valve (not shown) similar to the valve 1 1 1 is provided in the conduit 112.

An illustrative investment mold which can be cast using the apparatus of this invention is generally designated in FIG. 5 by reference numeral 120. The mold is comprised of a refractory body 121 having an opening 122, a central passage 123, and a plurality of pattern cavities 124 which are gated into the passage 123. As shown, a core 125 is positioned within the mold passage 123. The core 125, which may be formed of refractory material, has a closed end and an open end. A peripheral rim or step 126 is formed at the lower, open end of the core. The rim or step 126 serves to center the core 125 within the mold body 121 and substantially fills the passage 123 so that little or no molten metal can squeeze past the core when metal is cast into the mold. A refractory pouring basin or collar 127 is shown positioned on top of the mold 120 about its opening 122. The illustrated mold 120 includes a flask 128 around the mold body 121.

In using the apparatus 15 to cast metal into the mold 120, the air cylinder 44 is actuated to raise the track as sembly l7 and thereby lift the housing assembly 19 from the housing 18. This permits the housing assembly 19 to be rolled along the rail 40 to the broken line position illustrated in FIG. 1. When the housing assembly 19 has been moved away from the housing 18, the mold 120 is placed in the chamber 66 on the platform gasket 73 and the core 125 is positioned with its open end over the hole 74 of the platform 71. The pouring collar 127 is positioned on the mold and the mold chamber 66 is sealed around the mold. This is accomplished by a metal ring 130 which surrounds the upper end of the mold and is supported by a shoulder 131 of the houising 18. A rubber sealing ring 132 or the like is disposed between the ring 130 and the shoulder 131. The seal is completed by a ring 133 which rests on the upper end of the mold 120 and on the ring 130. The ring 133 is preferably made of asbestos or a similar material.

When the mold 120 has been positioned and sealed in the chamber 66, the housing assembly 19 is rolled along the rails 40 by means of an attached handle 135 to a location over the housing 18. The track assembly 17 is then lowered to place the housing assembly 19 into sealed engagement with the housing 18 on the gasket 88. Molten metal is then introduced into the ladle 95 through the opening 103 and, after the cover plate 104 has been replaced over the opening, the pouring chamber 65 is evacuated. The degree of vacuum in the chamber 65 can be varied depending upon such factors as the kind of metal beingcast, the amount of metal, the size of the mold, etc. A typical vacuum used for casting aluminum alloys is from 26 to 28 inches of mercury below atmospheric pressure. In accordance with conventional practice, the metal is usually degased prior to being placed in the ladle 95, and therefore the metal can be introduced into the mold 120 as soon as the desired vacuum has been produced in the chamber 65.

After the molten metal has been poured into the mold 120, the pressure in the pouring chamber 65 is raised, preferably by relieving the vacuum and opening the chamber to atmospheric pressure. Atmospheric pressure on the molten metal exposed in the mold opening 122 acts to force the molten metal into the mold cavities to promote a complete fill and aids in preventing draw-back as the metal subsequently solidifies.

The mold chamber 66 is evacuated prior to solidification of the metal in the mold and is preferably evacuated either before or at the same time that the vacuum is drawn in the pouring chamber 65. It may be desired to evacuate the chamber 66 first in order to shorten the time required to reduce the pressure in the chamber 65. Since the walls of the mold 120 are porous, the pouring chamber 65 can be evacuated faster if a vacuum has been previously drawn in the mold chamber. The metal in the mold opening 120 is maintained at atmospheric pressure and the vacuum applied to the outside of the mold is continued during at least partial solidification of the metal. The degree of vacuum in the chamber 66 which has been found sufficient to cast metal such as aluminum alloys is usually inches or more of mercury below atmospheric pressure. It is be lieved that the effectiveness of the vacuum around the mold may be the result of removing air from the pores of the mold and thereby preventing any such air from coming out of the pores prior to and during solidification of the metal. Whatever the explanation, it has been found that the application of the vacuum to the outside of the mold while the metal is under pressure through the mold opening results in production of sound castings which are free of defects.

Reference is now made to the embodiment of the invention shown in FIG. 6. The illustrated embodiment differs from the previously described embodiment 15 primarily in the provision of at least two spaced, lower housings 151, 152 on the support structure 153. Both of the lower housings 151, 152 are of the same construction as the housing 18 described in connection with FIGS. 1-5. The support structure 153 includes a track assembly 154 which is adapted to be raised and lowered adjacent each of the housings 151, 152. To this end, a pair of air cylinders 155 are mounted on the support structure 153 and have their piston rods connected to opposite ends of the track assembly 154. The track assembly 154 is comprised of a pair of rails 156 which are connected at their ends and extend on opposite sides of the lower housings 151, 152. Actuation of the cylinders 155 serves to elevate the track assembly 154 so that an upper housing assembly 157 can be moved from one end of the track assembly to the other over each of the lower housings 151, 152.

The upper housing assembly 157 is supported. for movement along the rails 156 by rail-engaging wheels 158. Cushioned stop assemblies 159 which are the same as the stop assemblies of the embodiment 15 are connected to the support structure 153 at the ends of the rails and serve to locate the upper housing assembly 157 over the lower housings 151, 152. The upper housing assembly 157 is identical in construction to the housing assembly 19 of the previously described embodiment of the invention and is cooperable with each of the lower housings 151, 152 to form a sealed enclosure as shown in FIG. 5. A vacuum line or conduit 160 extending from a suitable vacuum source is connected to the housing 151 in communication with the internal mold chamber, and another vacuum line 161 is connected to the housing 151 for evacuating the pouring chamber which is formed by cooperative engagement of the housing assembly 157 with the housing 151. A similar pair of vacuum lines 162, 163 are connected to the housing 152. All of the vacuum lines 160, 163 are provided with three-way valves which are actuatable to connect the chambers to the vacuum source and to the atmosphere.

The construction of the apparatus 150 is such that casting operations can be alternately carried out in the lower housings. When the upper housing assembly 157 has been moved to the right, as viewed in FIG. 6, a mold is mounted and sealed in the housing 151. The upper housing assembly 157 is then moved to the left along the rails 156 over the housing 151 and the track assembly is lowered to place the upper housing assembly in engagement with the housing 151, thereby forming a sealed enclosure. While the mold in the housing 151 is being cast in the manner previously described, another mold is mounted and sealed in the housing 152. When the casting operation in the housing 151 has been completed, the track assembly 154 is elevated by activation of both of the cylinders 155 and the upper housing assembly 157 is moved over the housing 152, whereupon the track assembly is again lowered to form a sealed enclosure with the housing 152. The mold in the housing 151 is removed and another mold is mounted and sealed in the housing so that the sequence of operations can be repeated when the mold in the housing 152 has been filled with metal.

FIGS. 7-9 show an embodiment of the invention which is especially suitable for casting ferrous metals.

The illustrated embodiment 175 is comprised of a support structure 16a including a track assembly 17a, and a lower housing 18a, all of which are identical in construction to the corresponding parts of the previously described embodiment of FIGS. 1-5. The pivotally mounted track assembly 17a is adapted to be raised and lowered adjacent the housing 18a by an air cylinder 44a.

An upper housing assembly 176 is supported for movement along the track assembly 170 by wheels 177.

The upper housing assembly 176 is similar to the housing assembly 19 previously described in connection with the embodiment shown in FIGS. l-S, and includes a cylindrical housing 178 having an upper end closed by a removable plate and an open lower end. The upper end of the housing 178 is provided with a window 179. A plate 180 is secured around the lower end of the housing 178 and is adapted to be supported by the flange 69a of the lower housing 18a. A sealing gasket 181 is provided between the flange 69a and the plate 180. The wheels 177 for supporting the housing assembly 176 are connected to the plate 180 by brackets 182.

As shown in FIG. 9, the housing 178 is cooperable with the lower housing 18a to form a sealed enclosure having an upper portion which defines a pouring or casting chamber 185 and a lower section which defines a mold chamber 186. The mold chamber 186 is adapted to be sealed from the pouring chamber 185 around the mold positioned within the housing 1821.

An induction melting furnace 187 is pivotally mounted in the pouring chamber 185 for pouring molten metal into a mold positioned in the mold chamber 186. The induction furnace 187 is of conventional construction and includes a crucible 188 and a primary electrical conductor and cooling coil I89 around the crucible. The furnace 187 is mounted for tilting movement by a metal strap 190 which surrounds the upper end of the crucible 188. The strap 190 is secured to a rod 191 which is journaled through the sides of the housing 178 and is provided with an external handle 192. The housing 178 is provided with a cover plate 193 which can be removed to charge the furnace 187.

An illustrative shell mold which can be cast using the apparatus 175 is generally designated by reference numeral 200. The mold 200 is comprised of a refractory shell 201 having an opening 202, a central passage 203, and a plurality of pattern cavities 204 which are gated into the passage 203. As shown, a core 205 is positioned within the mold passage 203. The core 205, which may be formed of refractory material, has a closed end and an open end. The assembly of the shell 201 and the core 205 is positioned on a gasket 206 supported by a platform 207. The open end of the core 205 is positioned over an opening 208 extending through the platform 207 and the gasket 206.

The mold chamber 186 is sealed around the mold 200 by structure including a metal plate 215 which is supported by a shoulder of the housing 18a. A rubber sealing ring 216 or the like is disposed between the ring 215 and the shoulder of the housing 180. The seal is completed by a ring 218 which rests on the upper end of the mold 200 and on the ring 215. The ring 218 is preferably made of asbestos or other similar material.

A vacuum line or conduit 220 (FIG. 7) is connected to the lower housing 18a in communication with the mold chamber 186. A three-way valve 221 is provided in the conduit 220 for connecting the mold chamber to a vacuum source or to the atmosphere. Another vacuum line or conduit 222 is connected to the lower housing 18a in communication with the pouring chamber 185. A three-way valve (not shown) similar to the valve 221 is provided in the conduit 222.

In operation of the apparatus 175, the mold 200 is mounted and sealed in the chamber 186 when the track assembly 17a is elevated and the housing assembly 176 is in the broken line position illustrated in FIG. 7. The upper housing assembly 176 is then rolled along the track assembly 17a to a location over the housing 180, and the track assembly is lowered to place the upper housing assembly 176 into sealed engagement with the housing 18a. After the induction furnace 187 has been charged, a vacuum is drawn in the pouring chamber 185. When the metal has been melted, the furnace is tilted by means of the handle 192 to cast the molten metal into the mold 200. After the molten metal has been poured into the mold 200, the pressure in the pouring chamber is raised, preferably by relieving the vacuum and opening the chamber to atmospheric pressure. Atmospheric pressure on the molten metal exposed in the mold opening 202 acts to force the mo]- ten metal into the mold cavities to promote a complete fill. A vacuum is drawn in the mold chamber 186 prior to solidification of the metal in the mold. The chamber 186 is preferably evacuated either before or at the same time that the pouring chamber 185 is evacuated. When the casting operation has been completed, the track assembly 17a is raised by actuation of the cylinder 44a so that the upper housing assembly 176 can be moved away from the lower housing 18a for another sequence of operations.

As will be apparent, the induction melting furnace 187 shown in FIG. 9 can be incorporated in the embodiments of the invention shown in FIGS. l-S and in FIG. 6. It will also be apparent that an apparatus similar to that shown in FIG. 6 can be constructed to include any desired number of lower housings and that the upper housing can be moved so as to successively cooperate with each of the lower housings.

Many other variations and modifications of the invention will be obvious to those skilled in the art in the light of the foregoing detailed disclosure. Therefore, it is to be understood that, within the scope of the appended claims, the invention can be practiced otherwise than as specifically shown and described.

What is claimed is:

1. Apparatus for casting molten metal into a mold having an opening into which the metal is introduced to fill the mold, said apparatus comprising:

a. first and second housing means cooperable to define a mold chamber and a pouring chamber,

b. means mounting at least one of said housing means for movement toward and away from the other housing means,

c. means for sealing said chambers from each other so that a difierent pressure can be maintained in said pouring chamber than in said mold chamber, said sealing means including means sealing said mold chamber around a mold positioned therein with the opening of the mold communicating with said pouring chamber,

d. means for introducing molten metal from said pouring chamber into the opening of the mold positioned in said mold chamber,

e. means for evacuating said pouring chamber so that the metal can be introduced into the mold while under vacuum applied to the mold opening and for thereafter permitting the pressure in said pouring chamber to be increased in order to increase the pressure applied through the mold opening to the molten metal in the mold, and

. means for evacuating said mold chamber to apply a vacuum to the outside of the mold and for maintaining the vacuum while the pressure in said pouring chamber is increased.

2. Apparatus for casting molten metal into a mold having an opening into which the metal is introduced to fill the mold, said apparatus comprising:

a. first and second housing means cooperable to define a mold chamber and a pouring chamber,

b. means mounting at least one of said housing means for movement toward and away from the other housing means,

c. means for sealing said chambers from each other so that a different pressure can be maintained in said pouring chamber than in said mold chamber, said sealing means including means sealing said mold chamber around a mold positioned therein with the opening of the mold communicating with said pouring chamber,

d. means for evacuating said pouring chamber in order to apply a vacuum to the mold opening,

e. means for introducing molten metal from said pouring chamber into the mold while under the vacuum applied to the mold opening,

f. means for increasing the pressure in said pouring chamber while the metal in the mold is still molten, and

g. means for evacuating said mold chamber to apply a vacuum to the outside of the mold and for maintaining the vacuum until the metal in the mold at least partially solidifies and while the pressure in said pouring chamber is increased.

3. Apparatus for casting molten metal into a mold having an opening into which the metal is introduced to fill the mold, said apparatus comprising:

a. housing means movable together to form a sealed enclosure having:

i. a lower portion defining a mold chamber adapted to receive a mold to be filled with metal,

ii. an upper portion defining a pouring chamber adapted to contain a supply of molten metal to be introduced into the mold,

b. means mounting parts of said housing means for relative movement toward and away from each other,

c. means for evacuating said chambers,

d. means for introducing molten metal from said pouring chamber into the opening of a mold in said mold chamber while under vacuum applied to the opening of the mold, and

e. means for permitting pressure to be applied to the opening of the mold after it has been filled with metal and while a vacuum is maintained in said mold chamber around the outside of the mold.

4. Apparatus as claimed in claim 3 wherein said mounting means comprises a track assembly, wheel means supporting a part of said housing means for movement along said track assembly, and actuating means for raising and lowering said track assembly.

5. Apparatus as claimed in claim 3 wherein said mounting means comprises a track assembly, wheel means supporting a part of said housing means for movement along said track assembly to a position over another part of said housing means, and means for raising and lowering said track assembly adjacent said another part of said housing means.

6. Apparatus for casting molten metal into a mold having an opening into which the metal is introduced to fill the mold, said apparatus comprising:

a. an upper housing means and at least two spaced lower housing means,

b. said upper housing means being selectively cooperable with each of said lower housing means to define a sealed enclosure having:

i. a lower portion defining a mold chamber adapted to receive a mold to be filled with metal,

ii. an upper portion defining a pouring chamber adapted to contain a supply of molten metal to be introduced into the mold,

c. means mounting said upper and lower housing means for relative movement so that said upper housing means can be selectively placed into sealed relation with each of said lower housing means,

d. means for sealing each of said mold chambers around the opening of a mold positioned therein with the opening of the mold exposed for communication with said pouring chamber, whereby a different pressure can be maintained in said pouring chamber than in said mold chambers,

e. means for evacuating each enclosure and for permitting the pressure in the pouring chamber of each enclosure to be increased while maintaining a vacuum in the mold chamber, and

f. means for introducing molten metal from the pouring chamber of each enclosure into the opening of a mold in the mold chamber while under vacuum applied to the opening of the mold.

7. Apparatus as claimed in claim 6 wherein said mounting means comprises a track assembly, wheel means supporting said upper housing means for movement along said track assembly to locations over said lower housing means, and actuating means for raising and lowering said track sssembly adjacent each of said lower housing means.

8. Apparatus for casting molten metal into a mold having an opening into which the metal is introduced to fill the mold, said apparatus comprising:

a. support structure including a track assembly and actuating means for raising and lowering said track assembly,

b. at least one lower housing secured to said support structure,

c. an upper housing cooperable with said lower housing to define a sealed enclosure having:

i. a lower portion defining a mold chamber adapted to receive a mold to be filled with metal,

ii. an upper portion defining a pouring chamber adapted to contain a supply of molten metal to be introduced into the mold,

d. means for evacuating each of said chambers and for permitting the pressure in said pouring chamber to be increased while maintaining a vacuum in said mold chamber,

e. means for introducing molten metal from said pouring chamber into the opening of a mold in said mold chamber while under vacuum applied to the opening of the mold, and

f. means supporting said upper housing for movement along said track assembly to a location above said lower housing when said track assembly is raised so that said upper housing can be lowered into cooperative engagement with said lower housing by lowering said track assembly.

9. Apparatus as claimed in claim 8 wherein said track assembly is pivotally mounted near one end at a location remote from said lower housing, and wherein said actuating means is connected to said track assembly for raising and lowering its opposite end.

10. Apparatus as claimed in claim 8 including a second lower housing connected to said support structure at a location spaced from said first-mentioned lower housing, said upper housing being movable along said track assembly to a location above said second lower housing and being cooperable therewith to form a second sealed enclosure, and wherein said actuating means is operable to raise and lower said track assembly adjacent each of said lower housings.

11. Apparatus for use in casting molten metal into a mold comprising:

a. upper and lower housings movable together to form a sealed enclosure,

b. said enclosure having an upper portion defining a pouring chamber and a lower portion defining a mold chamber adapted to be sealed from said pouring chamber around the mold,

0. means for permitting said chambers to be evacuated,

d. metal pouring means mounted in said pouring chamber,

e. means mounting said upper housing for movement toward and away from said lower housing,

f. said mounting means including a track assembly supported for swinging movement about a pivot axis at a location remote from said lower housing,

g. wheel means supporting said upper housing for movement along said track assembly to a position over said lower housing, and

h. actuating means for raising and lowering said track assembly adjacent said lower housing.

12. Apparatus for use in casting molten metal into a mold comprising:

a. support structure including a track assembly and actuating means for raising and lowering said track assembly,

b. a lower housing secured to said support structure,

0. said track assembly being pivotly mounted near one end at a location remote from said lower housing and said actuating means being connected to said track assembly for raising and lowering its opposite end, 1

d. an upper housing movable into engagement with said lower housing to form a sealed enclosure having an upper portion defining a pouring chamber and a lower portion defining a mold chamber adapted to be sealed from said pouring chamber around the mold,

e. metal pouring means supported in said upper houshaving an opening into which the metal is introduced to fill the mold, said apparatus comprising:

a. housing means cooperable to define a mold chamber adapted to receive a mold to be filled with metal and a pouring chamber for containing a'supply of molten metal to be introduced into the mold,

b. means mounting parts of said housing means for relative movement toward and away from each other,

c. means for sealing said mold chamber around the opening of a mold positioned therein,

d. means for evacuating said pouring chamber and for applying a vacuum to the opening of the mold in said mold chamber, whereby molten metal can be introduced under a vacuum into the mold opening to fill the mold,

6. means for evacuating said mold chamber to apply a vacuum to the outside of the mold, and

f. means for permitting pressure to be applied to the mold opening after the mold has been filled with metal, while maintaining the vacuum applied to the outside of the mold.

14. Apparatus for casting molten metal into a mold having an opening into which the metal is introduced to fill the mold, said apparatus comprising:

a. housing means defining a mold chamber adapted to receive a mold to be filled with metal and a pouring chamber for containing a supply of molten metal to be introduced into the mold,

b. means mounting parts of said housing means for relative movement toward and away from each other,

c. means for evacuating said pouring chamber and for applying a vacuum to the opening of a mold in said mold chamber, whereby molten metal can be introduced under a vacuum into the mold opening to fill the mold,

d. means for permitting pressure to be applied to the mold opening after the introduction of metal into the mold and while the metal in the mold is still molten, and

e. means for evacuating said mold chamber to apply a vacuum to the outside of the mold while maintaining the pressure applied to the mold opening until the metal in the mold at least partially solidifies.

15. Apparatus for use in casting molten metal into a mold and having an opening into which the metal is introduced to till the mold, said apparatus comprising:

a. housing means defining a mold chamber adapted to receive a mold to be filled with metal and a pouring chamber for containing a supply of molten metal to be introduced into the mold,

b. means for sealing said chambers from each other so that a different pressure can be maintained in said pouring chamber than in said mold chamber, said sealing means including means sealing said the pressure in the pouring chamber to be increased after the introduction of the molten metal into the mold while a vacuum is maintained in said mold chamber around the outside of a mold positioned therein, and v e. means mounting parts of said housing means for relative movement toward and away from each other. 

1. Apparatus for casting molten metal into a mold having an opening into which the metal is introduced to fill the mold, said apparatus comprising: a. first and second housing means cooperable to define a mold chamber and a pouring chamber, b. means mounting at least one of said housing means for movement toward and away from the other housing means, c. means for sealing said chambers from each other so that a different pressure can be maintained in said pouring chamber than in said mold chamber, said sealing means including means sealing said mold chamber around a mold positioned therein with the openiNg of the mold communicating with said pouring chamber, d. means for introducing molten metal from said pouring chamber into the opening of the mold positioned in said mold chamber, e. means for evacuating said pouring chamber so that the metal can be introduced into the mold while under vacuum applied to the mold opening and for thereafter permitting the pressure in said pouring chamber to be increased in order to increase the pressure applied through the mold opening to the molten metal in the mold, and f. means for evacuating said mold chamber to apply a vacuum to the outside of the mold and for maintaining the vacuum while the pressure in said pouring chamber is increased.
 2. Apparatus for casting molten metal into a mold having an opening into which the metal is introduced to fill the mold, said apparatus comprising: a. first and second housing means cooperable to define a mold chamber and a pouring chamber, b. means mounting at least one of said housing means for movement toward and away from the other housing means, c. means for sealing said chambers from each other so that a different pressure can be maintained in said pouring chamber than in said mold chamber, said sealing means including means sealing said mold chamber around a mold positioned therein with the opening of the mold communicating with said pouring chamber, d. means for evacuating said pouring chamber in order to apply a vacuum to the mold opening, e. means for introducing molten metal from said pouring chamber into the mold while under the vacuum applied to the mold opening, f. means for increasing the pressure in said pouring chamber while the metal in the mold is still molten, and g. means for evacuating said mold chamber to apply a vacuum to the outside of the mold and for maintaining the vacuum until the metal in the mold at least partially solidifies and while the pressure in said pouring chamber is increased.
 3. Apparatus for casting molten metal into a mold having an opening into which the metal is introduced to fill the mold, said apparatus comprising: a. housing means movable together to form a sealed enclosure having: i. a lower portion defining a mold chamber adapted to receive a mold to be filled with metal, ii. an upper portion defining a pouring chamber adapted to contain a supply of molten metal to be introduced into the mold, b. means mounting parts of said housing means for relative movement toward and away from each other, c. means for evacuating said chambers, d. means for introducing molten metal from said pouring chamber into the opening of a mold in said mold chamber while under vacuum applied to the opening of the mold, and e. means for permitting pressure to be applied to the opening of the mold after it has been filled with metal and while a vacuum is maintained in said mold chamber around the outside of the mold.
 4. Apparatus as claimed in claim 3 wherein said mounting means comprises a track assembly, wheel means supporting a part of said housing means for movement along said track assembly, and actuating means for raising and lowering said track assembly.
 5. Apparatus as claimed in claim 3 wherein said mounting means comprises a track assembly, wheel means supporting a part of said housing means for movement along said track assembly to a position over another part of said housing means, and means for raising and lowering said track assembly adjacent said another part of said housing means.
 6. Apparatus for casting molten metal into a mold having an opening into which the metal is introduced to fill the mold, said apparatus comprising: a. an upper housing means and at least two spaced lower housing means, b. said upper housing means being selectively cooperable with each of said lower housing means to define a sealed enclosure having: i. a lower portion defining a mold chamber adapted to receive a mold to be filled with metal, ii. an upper portion defining a pouring chamber adapted to contain a supply of molten metal to be introduced into the mold, c. means mounting said upper and lower housing means for relative movement so that said upper housing means can be selectively placed into sealed relation with each of said lower housing means, d. means for sealing each of said mold chambers around the opening of a mold positioned therein with the opening of the mold exposed for communication with said pouring chamber, whereby a different pressure can be maintained in said pouring chamber than in said mold chambers, e. means for evacuating each enclosure and for permitting the pressure in the pouring chamber of each enclosure to be increased while maintaining a vacuum in the mold chamber, and f. means for introducing molten metal from the pouring chamber of each enclosure into the opening of a mold in the mold chamber while under vacuum applied to the opening of the mold.
 7. Apparatus as claimed in claim 6 wherein said mounting means comprises a track assembly, wheel means supporting said upper housing means for movement along said track assembly to locations over said lower housing means, and actuating means for raising and lowering said track sssembly adjacent each of said lower housing means.
 8. Apparatus for casting molten metal into a mold having an opening into which the metal is introduced to fill the mold, said apparatus comprising: a. support structure including a track assembly and actuating means for raising and lowering said track assembly, b. at least one lower housing secured to said support structure, c. an upper housing cooperable with said lower housing to define a sealed enclosure having: i. a lower portion defining a mold chamber adapted to receive a mold to be filled with metal, ii. an upper portion defining a pouring chamber adapted to contain a supply of molten metal to be introduced into the mold, d. means for evacuating each of said chambers and for permitting the pressure in said pouring chamber to be increased while maintaining a vacuum in said mold chamber, e. means for introducing molten metal from said pouring chamber into the opening of a mold in said mold chamber while under vacuum applied to the opening of the mold, and f. means supporting said upper housing for movement along said track assembly to a location above said lower housing when said track assembly is raised so that said upper housing can be lowered into cooperative engagement with said lower housing by lowering said track assembly.
 9. Apparatus as claimed in claim 8 wherein said track assembly is pivotally mounted near one end at a location remote from said lower housing, and wherein said actuating means is connected to said track assembly for raising and lowering its opposite end.
 10. Apparatus as claimed in claim 8 including a second lower housing connected to said support structure at a location spaced from said first-mentioned lower housing, said upper housing being movable along said track assembly to a location above said second lower housing and being cooperable therewith to form a second sealed enclosure, and wherein said actuating means is operable to raise and lower said track assembly adjacent each of said lower housings.
 11. Apparatus for use in casting molten metal into a mold comprising: a. upper and lower housings movable together to form a sealed enclosure, b. said enclosure having an upper portion defining a pouring chamber and a lower portion defining a mold chamber adapted to be sealed from said pouring chamber around the mold, c. means for permitting said chambers to be evacuated, d. metal pouring means mounted in said pouring chamber, e. means mounting said upper housing for movement toward and away from said lower housing, f. said mounting means including a track assembly supported for swinging movement about a pivot axis at a location remote from said lower housing, g. wheel means supporting said upper housIng for movement along said track assembly to a position over said lower housing, and h. actuating means for raising and lowering said track assembly adjacent said lower housing.
 12. Apparatus for use in casting molten metal into a mold comprising: a. support structure including a track assembly and actuating means for raising and lowering said track assembly, b. a lower housing secured to said support structure, c. said track assembly being pivotly mounted near one end at a location remote from said lower housing and said actuating means being connected to said track assembly for raising and lowering its opposite end, d. an upper housing movable into engagement with said lower housing to form a sealed enclosure having an upper portion defining a pouring chamber and a lower portion defining a mold chamber adapted to be sealed from said pouring chamber around the mold, e. metal pouring means supported in said upper housing, f. means for permitting said chambers to be evacuated, and g. means supporting said upper housing for movement along said track assembly to a location above said lower housing when said track is raised so that said upper housing can be lowered into cooperative engagement with said lower housing by lowering said track assembly.
 13. Apparatus for casting molten metal into a mold having an opening into which the metal is introduced to fill the mold, said apparatus comprising: a. housing means cooperable to define a mold chamber adapted to receive a mold to be filled with metal and a pouring chamber for containing a supply of molten metal to be introduced into the mold, b. means mounting parts of said housing means for relative movement toward and away from each other, c. means for sealing said mold chamber around the opening of a mold positioned therein, d. means for evacuating said pouring chamber and for applying a vacuum to the opening of the mold in said mold chamber, whereby molten metal can be introduced under a vacuum into the mold opening to fill the mold, e. means for evacuating said mold chamber to apply a vacuum to the outside of the mold, and f. means for permitting pressure to be applied to the mold opening after the mold has been filled with metal, while maintaining the vacuum applied to the outside of the mold.
 14. Apparatus for casting molten metal into a mold having an opening into which the metal is introduced to fill the mold, said apparatus comprising: a. housing means defining a mold chamber adapted to receive a mold to be filled with metal and a pouring chamber for containing a supply of molten metal to be introduced into the mold, b. means mounting parts of said housing means for relative movement toward and away from each other, c. means for evacuating said pouring chamber and for applying a vacuum to the opening of a mold in said mold chamber, whereby molten metal can be introduced under a vacuum into the mold opening to fill the mold, d. means for permitting pressure to be applied to the mold opening after the introduction of metal into the mold and while the metal in the mold is still molten, and e. means for evacuating said mold chamber to apply a vacuum to the outside of the mold while maintaining the pressure applied to the mold opening until the metal in the mold at least partially solidifies.
 15. Apparatus for use in casting molten metal into a mold and having an opening into which the metal is introduced to fill the mold, said apparatus comprising: a. housing means defining a mold chamber adapted to receive a mold to be filled with metal and a pouring chamber for containing a supply of molten metal to be introduced into the mold, b. means for sealing said chambers from each other so that a different pressure can be maintained in said pouring chamber than in said mold chamber, said sealing means including means sealing said pouring chamber from said mold chamber around a mold positioned therein with the opEning of the mold communicating with said pouring chamber, c. means for evacuating said chambers so that the molten metal can be introduced into the mold while under a vacuum applied to the mold opening, and so that a vacuum can be applied to the outside of the mold during solidification of the metal therein, d. said means for evacuating being operable to permit the pressure in the pouring chamber to be increased after the introduction of the molten metal into the mold while a vacuum is maintained in said mold chamber around the outside of a mold positioned therein, and e. means mounting parts of said housing means for relative movement toward and away from each other. 